Micropile bearing plate

[HokieStructural]

I'm using the strut and tie procedure to design pile caps on 150-ton micropiles. In order to limit the stress on the nodal zones at top of piles (Section A.5.2), I'm forced to provide an 18.5"x18.5" bearing plate to develop the pile capacity. This is much larger than I'm used to seeing. A.5.2 does not allow an increase in strength due to confinement offered by the surrounding concrete in the pile cap. Is there a way to take advantage of the benefit of confinement and increase the allowable bearing stress at the top of the pile?

 

[civilperson]

Confinement with closed hoops or stirrups will allow higher limits in nodal zone.